The present invention relates to motor vehicle fuel tanks and particularly fuel tanks formed of plastic material and more particularly to plastic fuel tanks formed of plastic material not impervious to fuel vapor and having a vapor barrier associated with the wall of the tank to prevent permeation of fuel vapor through the tank wall.
Control of fuel vapor permeation through fuel tanks is now required on all vehicles operating on volatile hydrocarbon fuels in order to prevent fuel vapor from entering the atmosphere. The invention relates more particularly to plastic fuel tanks for motor vehicles having a vapor barrier layer embedded or molded in the plastic wall of the tank where the vapor barrier layer is typically formed of a dissimilar plastic material from that of the tank wall structure.
Where it is necessary to provide an aperture in the tank wall for attachment of fittings to the tank, it has been found that when the aperture is formed in the tank wall the break in the vapor barrier creates an area where fuel vapor can permeate through the wall of the tank and escape to the atmosphere. Accordingly, it has been desired to provide a way or means of attaching valves and fittings which pass through an aperture in the wall of a tank having an imbedded vapor barrier in a manner which prevents permeation and escape of vapor through the area of the aperture upon attachment of a fitting thereto. It has also been desired to provide a way or means for mechanically attaching a pass-through fitting to the tank and to provide a vapor impervious connection without the necessity of weldment of the pass-through to the tank.